Compression-rheostat



T. SPOONER.

COMPRESSION-RHEOSTAT. APPiICATlON FILED MAY 14, 1920.

1,398,605. PatentedNov. 29, 1921.

WITNESSES:

INVENTOR 6 62/ W 7 7720mm" Spoaner umrEo sures PATENT OFFICE,

THOMAS SPOONER, OF PITTSBURGH, ASSIGNOB TO WESTINGHOUSE ELECTRIC AND IANUFACTUBIN G COMPANY, A CORPORATION OF PENNSYLVANIA.

COIPBESSION-BEEOSTAT.

To all whom it may concern:

Be it known that I, THOMAS Sroom, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Penns lvania, have invented a new and useful improvement in Compression-Rheostats, of which the following is a specification.

My invention relates to compression rheo stats such as are commonly used .in connection with electrical circuits to vary the resistance thereof.

The object of my invention is to provide a rehostat of simple design, that may be relatively inexpensive in construction, of great durability, that is compact and has a wide range of resistance.

Heretofore, it has been customary to provide compression rheostats with radiating plates for cooling the blocks of resistance material. If there were a number of compression rheostats combined, it was difiicult to subject them to uniform stress and to maintain the plates and blocks of resistance material in alinement, thereby causing excessive heating at points where the contact is poor. Another diiiiculty in the use of compression rheostats is the tendency of the blocks of resistance material to break and crumble because of variations in temperature and pressure therein.

According to my invention I provide a rheostat in which blocks of resistance material and radiatin plates are so shaped and mounted that t eir surfaces are main- -tained in substantially uniform contact when they are subjected to compression. Means are provided also for equalizing the pressure upon a plurality of rheostats.

Briefly speaking, my invention consists in providing annular resistors which are mounted upon a rod and separated from each other by concave radiating plates. These concave plates aid in positioning the resistors and in cooling them. The pressure upon each rheostat is equalized by a slidably mounted plate being brought against the rheostats and applying pressure to its center by means of a rotatably mounted screw.

Reference may now be had to the accom-- panying drawings, Figure 1 of which is a view, in side elevation, of a plurality of rheostats constructed in accordance with my invention. Fig. 2 is a view, in end elevation, of the rheostat shown 111 Fig. 1. Figs. 3.

Specification of Letters Patent.

Application filed Kay 14,

. which the rheostats shown in ample, as mioarta, on which are 'cated upon the 7 plate 18 Patented Nov. 29, 1921. 1920. Serial No. Samoa.

and 4 are detail'views, in end elevation and 1n slde elevation, respectively, of one of the resistor elements shown in Fi s. 1 and 2. Figs. 5 and 6 are detail views, in end elevatlon, and in side elevation, respectively, of the radiating plate shown in Figs. 1 and 2. Fig. 7 1s a diagram showing the manner in Figs. 1 and 2 are so connected electrically that they may be operated in series or in parallel.

Referring particularly to Figs. 1 and 2, 21"1'6S1Shfi1108 device 1 or rheostat comprises a plurality of smaller rheostats 2, 3 and 4 that are mounted upon a support or base 5 of suitable insulating material, such, for example, as slate or micarta. The rheostats are secured to the base 5 by means of triangular end plates 6 and 7 and bolts 8. Bindingposts 9 and 10 are provided for connectlng the rheostat 1 to any desired electrical circuit. A switch 11, which is mounted upon the base 5, is employed to arrange the electrical connections of the, rheostats 2, 3 and 4 either in series or in parallel relation.

Each of the rheostats 2, 3 and 4 comprises i a metal rod 12 surrounded by a tube 13 of suitable insulating material, such, for exslidably mounted annular resistors 14; of suitable resistance material, such, for example, as carbon. Copper radiating plates 15 are also mounted upon the tube 13 alternating with the annular resistors 14. The rods 12 are secured to the end 16 and washers 17.

A plate 18 of triangular shape, which is slidably mounted upon the rods 12 and the tubes 13, is actuated by a screw 19, which is rotatablymounted in the end plate 7.

annular projection 20 is centrally loin order that the pressure of the screw 19, by which it is plates 6 and 7 by nuts engaged, will always be applied to the the conductivity of the rheostats 2, 3 and 4.

The rheostats 2 and 3 are electrically con.

nected by a copper strip 21 and the rheostats 3 and 4 are likewise connected by a strip 22. The copper strips 21 and 22 are electrically connected b conductors 23 and 24, respectively, to t e switch 11. The rheostats 2 and 4 are electrically connected to binding posts 10 and 9, resplectively, by conductors '25 and 26. Only t e portions of the conductors 23, 24, 25 and 26 are shown that are above the base 5, the remaining portion bein concealed in grooves 111 the base 5; Insu ating washers 27 and 'metalzwashers 28 are mounted on the rods 12 between the end plate 6 and resistors 2, 3 and 4. The

late 18 is insulted from rheostats 2,3 and 4 y annular washers 29.

In Figs. 3 and 4, is shown one of the annular resistors 14 provided with a hole 30 for mounting upon one of the tubes 13.

Referrm to Figs. 5 and 6, one of the radiating p ates 15 is rovided with a circular base portion 31, t e inside diameter of which is slightly greater than the outside diameter of the disk 14. The annular rim portion 32 is provided for positioning the resistor 14 and for preventing portions thereof from falling out should it become cracked. The plate 15 is provided with a hole 33 for mounting it upon one of the tubes 13.

Fig. 7 is a diagram of the electrical circuits embodying the rheostats 2, 3 and 4, conductors 23, 24, 25 and 26 and the switch 11. The wiring diagram clearly indicates that the resistors 2, 3 and 4 are connected in series when the switch 11 is open and in parallel when it is closed.

It will be observed by those skilled in the art that by my invention, I provide a rheostat in which any increased pressure caused by the expansion of the resistors 14 and radiatin plates 15, when they become heated, is practically compensated for by the expansion of the-rods 12, and thus the resistance of the rheostats 2, 3 and 4 will remain approximately constant when they are in use, without adjusting the screw 19.

While I have shown my invention in the preferred form, it is capable of'being subjected to slight/modifications which do not depart from the spirit thereof; therefore, I

desire only to be limited by the scope of the appended claims.

I claim as my invention,

1. In a compression rheostat, the combination with a self-sustaining resistor, of a radiating plate that only partially surrounds said resistor.

2. In a rheostat, the combination with a self-sustaining resistor, of a radiating plate having a portion of its surface conforming to the corresponding surface of said resistor and having a flange portion which partially inclose the sides thereof. I

3. In a rheostat, the combination with a rod and a resistor mounted thereon, of a radiating plate mounted upon said rod and substantlall surrounding said resistor.

4. In a r eostat, the combination with a holding member and a resistor mounted thereon, of a plate movably mounted upon said holding member and provided with. a rim portion that partially surrounds said resistor.

5. In a compression rheostat, the combination with a rod and a plurality of resistors mounted thereon, of a plurality of plates mounted alternately with said resistors upon said rods and severally provided with flange portions that partially surround said resistors.

6. In a compression rheostat, the combination with a rod and a plurality of annular resistors mounted thereon, of a plurality of annular plates mounted alternately with said resistors upon said rod, each of which is provided with an annular portion that partially incloses said resistor.

7 In a rheostat, the combination with a self-sustaining resistor, of a radiating plate havin a concave portion partially surrounding said resistor.

8. In a rheostat, the combination with a plurality of self-sustaining resistors, of a plurality of radiating plates placed between said resistors, each of said plates having a concave portion partially surrounding a resistor.

9. In a rheostat, the combination with a plurality of self-sustaining resistors, of radiating plates spaced alternately with said resistors, each of said plates having a hollow portion partially inclosing a resistor, said plates and said resistors being unattached one to the other.

10. In a rheostat, the combination with a rod, of a plurality of resistors slidably mounted upon said rod, a plurality ofradiating plates slidably mounted upon said rod and spaced alternately with said resistors, eachof said plates having a hollow portion partially surrounding a resistor, and means for applying pressure to said resistors and said plates.

In testimony whereof, I have hereunto subscribed my name this fourth" day of May,

THOMAS SPGONER. 

